研究者詳細 - 池田　直

論文 - 池田　直

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Possibility of magnetoelectric effect in antiferromagnetic rfe2o4

Naoshi Ikeda, Kazuhiro Saito, Kay Kohn

Ferroelectrics 161 ( 1 ) 111 - 115 1994年1月

掲載種別：研究論文（学術雑誌）

We report the magnetoelectric effect of a polycrystalline sample of a triangular Ising antiferromagnet ErFe2O4-8, in which the existence of short range charge ordering was inferred from the neutron and dielectric studies. The sign of the magnetoelectric signal was reversed at 77 K, when the electric or magnetic field was applied in the opposite directions during cooling the specimen down to 77 K. The sign of the signal was independent of the direction of the static bias magnetic field in the range above 150 K. The signal was maximum at 183 K. We suggest a relation between the origin of the magnetoelectric effect and the dielectric relaxation due to an electron hopping between Fe3+ and Fe2+ sites. © 1994, Taylor & Francis Group, LLC. All rights reserved.

DOI： 10.1080/00150199408213359

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Dielectric Relaxation and Hopping of Electrons in ErFe204

Naoshi Ikeda, Kay Kohn, Hijiri Kito, Jun Akimitsu, Kiiti Siratori

Journal of the Physical Society of Japan 63 ( 12 ) 4556 - 4564 1994年

掲載種別：研究論文（学術雑誌）

We report the frequency and the temperature dependence of the dielectric constant of polycrystalline ErFe2O4-δ with different degrees of oxygen deficiency S. a large dielectric relaxation, with the order of magnitude of 104 and nearly of the Debye type, is observed in the magnetically ordered states within the temperature and frequency ranges of 150 k to 290 K and 1 kHz to 3 MHz, respectively. The dispersion is larger in the sample with more oxygen deficiency. From the temperature dependence of the characteristic frequency, we conclude that the elementary process of the dispersion is related to electron hopping between Fe2+ and Fe3+ ions. a large value of the dielectric constant is consistent with the existence of spontaneous polarization in the magnetic phases of this oxide. We propose that the motion of the polarization domain boundaries is a determining factor of low-frequency dielectric constant. © 1994, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

DOI： 10.1143/JPSJ.63.4556

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Cd substitution effect on the superconducting transition temperature in RE<inf>1-x</inf>Cd<inf>x</inf>Ba<inf>2</inf>Cu<inf>3</inf>O<inf>y</inf>

Naoshi Ikeda, Sadao Higuchi, Kay Kohn

Phase Transitions 41 ( 1-4 ) 209 - 215 1993年1月

掲載種別：研究論文（学術雑誌）

We report the change of the superconducting transition temperature Tc with the substitution of rare earth with cadmium in the RE1-xCdxBa2Cu3Oy system, where RE is Nd, Eu, Gd, Dy and Y. The decrease of Tc with the amount of Cd was found to be closely related to the radius of the RE3+ ion. © 1993, Taylor & Francis Group, LLC. All rights reserved.

DOI： 10.1080/01411599308207781

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A simple alternating current magnetometer for high temperature superconductivity study

Naoshi Ikeda, Kay Kohn

Phase Transitions 42 ( 1-2 ) 7 - 14 1993年1月

Spin-glass behavior in amorphous BiFeO3 査読

Shin Nakamura, Susumu Soeya, Naoshi Ikeda, Midori Tanaka

Journal of Applied Physics 74 ( 9 ) 5652 - 5657 1993年

記述言語：英語掲載種別：研究論文（学術雑誌）

Short-range antiferromagnetic (speromagnetic) behavior was observed for amorphous BiFeO3 by static magnetic measurements, ac susceptibility (χac) measurement, and 57Fe Mössbauer spectra measurements. The magnetic behavior is classified into three temperature ranges: (i) paramagnet for T≳220 K
(ii) local clustering of spins for 20 K&lt
T&lt
220 K
and (iii) speromagnet in which all spins are frozen into random directions for T&lt
20 K. In the spin freezing state the magnetization shows irreversibility and the χac-T curve has a cusp. The variation of the spin freezing temperature against measuring magnetic field and measuring frequency indicate that the speromagnetic order is very similar to that of spin glass.

DOI： 10.1063/1.354179

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Effect of Pr substitution on superconductivity in (PrxY1−x)Ba2Cu4O8

Nobuyoshi Yamada, Zhen Guo, Naoshi Ikeda, Kay Kohn, Takeo Iri, Ken Ichiro Gondaira

Physica C: Superconductivity 185-189 809 - 810 1991年12月

A Simple Alternating Current Magnetometer of the Automatic Balancing Type

Ikeda Naoshi, Kohn Kay

Jpn J Appl Phys 29 ( Part 1, No. 1 ) 208 - 209 1990年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：社団法人応用物理学会

An improvement of a Hartshorn type alternating current magnetometer is reported. The use of a dual channel oscillator, a two-phase lock-in amplifier and a personal computer enabled us to obtain a simple feedback system for automatic balancing of the bridge. The resolution of this system is about $3\times 10^{-7}$ emu of magnetic moment or higher at the field of 0.8 Oe in amplitude and 159 Hz in frequency.

DOI： 10.1143/jjap.29.208

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Suppression of superconductivity by lanthanum substitution in the Bi4Ca3Sr3Cu4Oy system

N. Ikeda, K. Kohn, E.V. Sampathkumaran, R. Vijayaraghavan

Solid State Communications 68 ( 1 ) 51 - 55 1988年10月

Influence of chemical substituents on the superconductivity of the system Bi4Ca3Sr3Cu4Oy

E V Sampathkumaran, N Ikeda, K Kohn, R Vijayaraghavan

Journal of Physics F: Metal Physics 18 ( 8 ) L163 - L167 1988年8月

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